The invention relates to an x-ray diagnostic apparatus with an image-intensifier-TV chain as well as a control installation for the dose rate of the x-ray tube and thus the mean brightness of the output image of the x-ray image intensifier.
An x-ray diagnostic apparatus of this type, for example, is described in U.S. Pat. No. 3,991,314. In such an x-ray diagnostic apparatus, the desired rated value for the dose rate of the x-ray tube is adjusted for an exposure. In so doing, in practice, only such dose rates are programmed as rated values, which allow a good diagnosis.
In an x-ray diagnostic apparatus of the type initially cited, the image-intensifier-TV chain is used not only for diagnosis but rather also for positioning the patient before an x-ray exposure. On the basis of the fluoroscopy image, the organs to be photographed can be correctly located very quickly reliably. By adjusting the patient with fluoroscopy monitoring, the occurrence of useless photographic exposures is avoided. The patient and the physician, thus, are less exposed to radiation than in the case of the adjustment of the patient for an x-ray photographic exposure without fluoroscopy monitoring, since in this case x-ray exposures must often be repeated.
Positioning the patient with fluoroscopy monitoring, however, also demands a certain dose, which leads to a certain exposure of the patient.